Anisotropy in Geoelectromagnetism: (Methods in Geochemistry and Geophysics)

This comprehensive treatise is the first to be devoted solely to the study of the effect of electrical anisotropy in the propagation of electromagnetic waves in the earth. The book handles a wide range of local, regional and global geophysical problems. It also provides analytical solutions to complex physical situations, related numerical results, and graphic displays for many fundamental and applied problems. The following specific problems of solid-earth relevance are discussed in detail: direct-current mapping of anisotropic sedimentary formations; anisotropic effects in well-logging measurements; mutual impedance measurements (frequency and time domain) in induction prospecting on the anisotropic earth; low-frequency communication in anisotropic coal mines; crustal mapping by magnetotellurics for a layered dipping anisotropic and inhomogeneous earth; deep electromagnetic sounding in areas of geodynamic interest; numerical modelling of laterally inhomogeneous anisotropic conductors; data interpretation by inversion techniques for anisotropic media; and laboratory and field results on anisotropic formations.

Table of Contents:
1. General Introduction to Anisotropy and Geoelectromagnetism. A. Anisotropy. Introduction. Historical development of anisotropy studies. Anisotropic earth. Mathematical representation. Anisotropy in electrical conductivity. Some significant observations motivating anisotropy studies. Geoelectrical studies on anisotropy. B. Geoelectromagnetism. Introduction. Geoelectromagnetic methods. Geophysical structures and analytical methods. Analytical statement of a general induction problem. 2. Electrical Anisotropy in Direct-Current Resistivity Measurements. Introduction. Electrical potential over a homogeneous earth. Anisotropic earth. Two-layered anisotropic earth. Kernel function for a n-layered anisotropic earth. Apparent resistivity for an embedded anisotropic homogeneous layer (three layered model). Anisotropic inhomogeneous layer. Dipping anisotropic earth. Equivalent isotropic models for anisotropic situations. Dar-Zarrouk variables and functions. Depth of investigations over an anisotropic half-space. Tri-potential measurements over a two-layered anisotropic earth. Electrical anisotropic effects on ``mise a la masse'' E surveys. Anisotropy effects on resistivity-logging measurements. 3. Electromagnetic Depth Sounding by Dipolar Sources Over an Anisotropic Earth. A.Introduction. B. Vertical electric dipole on an anisotropic half-space. C. Horizontal electric dipole over an anisotropic half-space. D. Mutual coupling of current wires placed on the anisotropic earth. E. Electromagnetic sources buried in an anisotropic region. F. Transient coupling (between finite current sources placed on anisotropic conducting half-space). 4. Anisotropy Effects in Magnetotelluric Probing. Magnetotellurics. 5. Some Relevant Anisotropic Studies. Analog model studies. Numerical models. Physical properties of rocks. The inverse problem. 6. Geophysical Applications and Field Observations Related to Electrical Anisotropy. A. Applications of studies on electrical anisotropy. B. Geophysical field observations related to anisotropic formations. C. Concluding remarks. Subject Index.